Legal frequencies/power in the US for FPV ?

I'm new to FPV and have been reading a lot and asking questions on these forums. I've asked the question about legal frequencies and power limits for FPV in the US on at least three of these forums, and I've gotten different answers from each. I don't have an Amateur Radio Operator's license, and I suspect that many who participate on these forums don't have one either. There seems to be definite disagreement or misunderstanding about this topic by many. Regarding maximum allowed power on 900Mhz, I've gotten answers from 10mw to 25mw up to 500mw. I'm confident that 900mhz, 2.4mhz and 5.8mhz is allowed for non-hams in the US, but I have no idea of the max power output allowed.

Is it possible that the non-hams on these forums don't know either, and just go ahead and buy 500mw and higher transmitters from China? How many FPV users are unintentionally exceeding transmiting limits of the AV equipment? As the hobby increases in popularity, there has to eventually be a day of reckoning.